STAINLESS STEEL GRADE 310S (UNS S31008 / W.NR. 1.4845) — COMPREHENSIVE TECHNICAL DATASHEET
Stainless Steel Grade 310S (UNS S31008 / W.Nr. 1.4845) is a highly alloyed, austenitic heat-resisting stainless steel engineered for structural stability, oxidation resistance, and mechanical integrity in extreme high-temperature environments. Representing the low-carbon modification of standard AISI 310, this grade is specifically optimized for fabricated and welded assemblies.
By restricting the carbon content ($\le 0.08\%$), the alloy suppresses the kinetics of sensitization and localized intergranular corrosion that typically plague high-carbon grades during thermal exposure or welding. The material is widely standardized across major international regulatory frameworks, facilitating its seamless integration into high-temperature process equipment, petrochemical systems, and power generation boilers.
■ Global Standard Specifications
Grade 310S is globally codified across multiple standards, verifying its material boundaries for pressure vessels, line piping, structural bars, and high-performance aerospace components.
| Standard Body | Grade Name / Designation | Product Specification Standards |
|---|---|---|
| UNS (USA) | S31008 (Low Carbon Variant) | ASTM A240, ASTM A276, ASTM A312, ASTM A479 |
| EN (Europe) | 1.4845 (X8CrNi25-21) / 1.4951 | EN 10095 (Heat-Resisting), EN 10296-2 |
| JIS (Japan) | SUS310S | JIS G4303, JIS G4304, JIS G4305, JIS G3459 |
| AMS (Aerospace) | UNS S31008 | AMS 5523 (Sheet/Plate), AMS 5651 (Bars/Forgings) |
| ASME (Boiler / PV) | SA 310S (UNS S31008) | ASME SA240, ASME SA276, ASME SA312, ASME SA479 |
| GOST (Russia) | 10Kh23N18 / 10Ch23N18 | GOST 9940-81, GOST 9941-81 |
| GB (China) | 06Cr25Ni20 | GB/T 4237 |
■ Chemical Composition Limits (Weight %)
The microstructural stability and high-temperature environmental resistance of SS 310S are governed by a highly controlled chemistry balanced between ferrite-promoting chromium and austenite-stabilizing nickel.
| Element | ASTM A240 / UNS S31008 | EN 10095 / W.Nr. 1.4845 | JIS G4304 / SUS310S | Typical Values |
|---|---|---|---|---|
| Chromium (Cr) | 24.00 – 26.00 | 24.00 – 26.00 | 24.00 – 26.00 | 25.50 |
| Nickel (Ni) | 19.00 – 22.00 | 19.00 – 22.00 | 19.00 – 22.00 | 19.10 |
| Carbon (C) max | 0.080 | 0.100 | 0.080 | 0.050 |
| Silicon (Si) max | 1.500 | 1.500 | 1.500 | 0.500 |
| Manganese (Mn) max | 2.000 | 2.000 | 2.000 | 1.650 |
| Phosphorus (P) max | 0.045 | 0.045 | 0.045 | 0.025 |
| Sulfur (S) max | 0.030 | 0.015 | 0.030 | 0.005 |
| Nitrogen (N) max | — | 0.110 | — | 0.040 |
■ Proprietary Datasheet Download
For piping engineers, plant metallurgists, and structural detailers requiring granular stress simulation criteria, ASME Section VIII wall sizing equations, and advanced scaling charts, the complete technical manual can be accessed.
Alloy 310S — Comprehensive High-Temperature Technical Datasheet
Contains empirical metrics for finite element modeling, long-term stress-rupture curves, and certified welding procedures. Engineering credentials required.
⬇ DOWNLOAD DATASHEET■ Physical and High-Temperature Thermophysical Properties
Austenitic stainless steels feature high thermal expansion coefficients and low thermal conductivity compared to standard carbon steels, generating intense transient localized thermal stresses. Liquid quenching lines are strictly discouraged.
| Physical Constants | Metric Value | Imperial Value |
|---|---|---|
| Density (Ambient) | 7.89 – 8.03 g/cm³ | 0.284 – 0.290 lb/in³ |
| Melting Range | 1354°C – 1402°C | 2470°F – 2555°F |
| Specific Heat Capacity (0 – 100°C) | 500 – 502 J/kg·K | 0.12 BTU/lb·°F |
| Poisson's Ratio | 0.27 – 0.30 | 0.27 – 0.30 |
| Relative Magnetic Permeability | ≤ 1.02 (Annealed) | ≤ 1.02 (Annealed) |
The non-linear variations of thermophysical constants across an escalating thermal envelope are indexed below:
| Temperature Threshold | Modulus of Elasticity (GPa / Simple Mpsi) | Mean Coeff. of Thermal Expansion (×10⁻⁶ K⁻¹) | Thermal Conductivity (W/m·K) | Electrical Resistivity (μΩ·cm) |
|---|---|---|---|---|
| 20°C / 68°F | 196 – 200 / 28.5 – 29.0 | — | 14.2 | 72.0 – 78.0 |
| 100°C / 212°F | — | 15.9 | 14.2 | — |
| 315°C / 600°F | — | 16.2 | — | — |
| 538°C / 1000°F | 158.6 / 23.0 | 17.0 | 18.7 (at 500°C) | — |
| 649°C / 1200°F | 150.3 / 21.8 | 17.6 | — | 114.8 |
| 800°C / 1472°F | — | 18.5 | 21.5 | 122.0 |
| 1000°C / 1832°F | — | 19.0 | 23.0 | 128.0 |
■ Mechanical Properties Profile (Ambient & High Temp)
| Specification / Temperature Threshold | Yield Strength (0.2% Offset) | Ultimate Tensile Strength (UTS) | Elongation (A₅) | Hardness Maximum |
|---|---|---|---|---|
| ASTM A240 Plate (20°C) | ≥ 205 MPa (≥ 30.0 ksi) | ≥ 515 MPa (≥ 75.0 ksi) | ≥ 40% | ≤ 217 HBW / ≤ 95 HRB |
| EN 10095 Plate (20°C) | ≥ 210 MPa (≥ 30.5 ksi) | 500 - 700 MPa | ≥ 33 - 35% | ≤ 192 HBW |
| JIS G4304 Plate (20°C) | ≥ 205 MPa (≥ 30.0 ksi) | ≥ 520 MPa | ≥ 40% | ≤ 187 HBW / ≤ 225 HV |
| Elevated 538°C (1000°F) | 143.4 MPa (20.8 ksi) | 467.5 MPa (67.8 ksi) | 47% | — |
| Elevated 649°C (1200°F) | 142.7 MPa (20.7 ksi) | 373.0 MPa (54.1 ksi) | 43% | — |
| Elevated 760°C (1400°F) | 133.1 MPa (19.3 ksi) | 242.0 MPa (35.1 ksi) | 46% | — |
| Elevated 871°C (1600°F) | 84.1 MPa (12.2 ksi) | 131.7 MPa (19.1 ksi) | 48% | — |
■ High-Temperature Creep and Stress-Rupture Strength
Above 550°C, time-dependent plastic creep governs structural boundaries. Apparent activation energies ($Q_c$) within this multi-element matrix average 307 kJ/mol, tracking dislocation climb-assisted glide constraints.
| Temperature | 1% Creep Limit (10,000 h) | Stress to Rupture (1,000 h) | Stress to Rupture (10,000 h) | Stress to Rupture (100,000 h) |
|---|---|---|---|---|
| 600°C (1112°F) | 90 MPa (13.0 ksi) | 170 MPa | 130 MPa | 80 MPa |
| 700°C (1292°F) | 30 MPa (4.3 ksi) | 80 MPa | 40 MPa | 18 MPa |
| 800°C (1472°F) | 10 MPa (1.45 ksi) | 35 MPa | 18 MPa | 7 MPa |
| 900°C (1652°F) | 4 MPa (0.58 ksi) | 15 MPa | 8.5 MPa | 3 MPa |
■ Environmental Corrosion and Atmosphere Compatibility Boundaries
| Atmosphere / Environment | Max Recommended Service Limit | Primary Metallurgical Degradation Mechanism |
|---|---|---|
| Continuous Clean Air | 1150°C (2100°F) | Thermodynamic growth of passive, uniform chromia scale. |
| Intermittent / Cyclic Air | 1035°C (1900°F) | CTE mismatch strains induce micro-cracking and spallation. |
| Oxidizing Low-Sulfur ($\le 2 \ \text{g/m}^3$) | 1050°C (1922°F) | Competitive sulfur-oxygen reactions; manageable internal sulfidation. |
| Oxidizing High-Sulfur ($> 2 \ \text{g/m}^3$) | 950°C (1742°F) | Sulfur breaks scale layer, forming low-melting nickel-sulfur eutectics. |
| Carburizing / Nitriding Gas | 850°C – 950°C | Carbon absorption forms internal networks, choking room-temp ductility. |
| Stagnant Chloride Water | Restricted (Not Recommended) | Absence of Molybdenum gives low PREN ($\sim 25$), risking pitting. |
■ Fabrication, Heat Treatment, and Weld Joint Engineering
- Solution Annealing (+AT): Heat uniformly between 1040°C and 1150°C (1900°F to 2100°F). Soaking time tracks a minimum of 30 minutes per inch of maximum section bounds. Quench rapidly in water to maintain all alloy bounds in solid solution.
- Sigma Phase Microstructural Instability: Long-term operations inside the 650°C – 900°C range prompt delta-ferrite to decompose into the hard, intermetallic sigma ($\sigma$) phase. This causes severe room-temperature embrittlement, though it stays benign at heat. Interfacial boundaries are audited quantitatively via electrolytic 10% oxalic acid etching.
- Weld Hot-Cracking Protection: fully austenitic weld deposits have minimal trace solubility for P and S impurities, causing thin liquid films to segregate to grain boundaries during cooling. To prevent solidification cracking, eliminate preheating, limit heat inputs below 1.0 kJ/mm, restrict interpass targets below 150°C, and balance the weld pool to maintain a minor ferrite content (3 to 10 FN). Pair with ER309L wires when joining to carbon steels.
■ ASME Section VIII Pressure Boundary Sizing Criteria
Per Section VIII Division 1 (Paragraph UG-27), the required minimum wall thickness ($t$) of a cylindrical shell under circumferential tension is calculated using the material allowable stress limit ($S$) from Section II Part D:
Where $P$ represents internal design pressure, $R$ is shell inside radius, and $E$ is joint efficiency (E=1.0 for full radiography, E=0.85 for spot radiography, E=0.70 for non-destructive check omissions). Note: High-strength allowable stress data points permit yield criteria utilizations up to 90% at heat, but may cause minor permanent deformation limits; avoid using these limits in precision gasketed configurations.